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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 532 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

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  1. 1.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  2. 2.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 13 cm, 11 cm and 9 cm? (a) No (b) Yes
  5. 5.The two interior opposite angles of a triangle are 27° and 34°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 12 cm, 3 cm and 9 cm? (a) No (b) Yes
  7. 7.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  11. 11.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 95° and angle B = 45°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 6 cm, 5 cm and 12 cm? (a) Yes (b) No
  15. 15.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  17. 17.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  18. 18.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  19. 19.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  22. 22.Can a triangle have sides of 4 cm, 10 cm and 2 cm? (a) Yes (b) No
  23. 23.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  26. 26.Can a triangle have sides of 8 cm, 18 cm and 12 cm? (a) Yes (b) No
  27. 27.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 41° and 55°. What is the exterior angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  32. 32.Can a triangle have sides of 8 cm, 4 cm and 6 cm? (a) No (b) Yes
  33. 33.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 21° and 35°. What is the exterior angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  36. 36.Can a triangle have sides of 10 cm, 5 cm and 8 cm? (a) Yes (b) No
  37. 37.Can a triangle have sides of 9 cm, 10 cm and 20 cm? (a) No (b) Yes
  38. 38.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 44° and angle B = 110°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?

Answer key

  1. 15
  2. 70
  3. 43
  4. Yes
  5. 61
  6. No
  7. 56
  8. 62
  9. 43
  10. 13
  11. 25
  12. 28
  13. 40
  14. No
  15. 68
  16. 10
  17. 24
  18. 26
  19. 22
  20. 130
  21. 21
  22. No
  23. 36
  24. 30
  25. 40
  26. Yes
  27. 20
  28. 96
  29. 57
  30. 114
  31. 12
  32. Yes
  33. 79
  34. 56
  35. 100
  36. Yes
  37. No
  38. 10
  39. 26
  40. 50

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